Athlon 6400 x2 has better performance than phenom at gaming when all 4 cores are not utilized (most cases) . So if he is a gamer and wants to buy an Amd processor, at this point 6400 x2 is better than any phenom at gaming.
__________________
System Specifications: Athlon64 3200+ @ 2,12 ghz, 1GB DDR RAM, 9600GT 512MB, 200+250 GB HD, Windows xp sp3